Aspirin Not Effective in Preventing Strokes in Patients With Atrial Fibrillation

In Atrial Fibrillation, the irregular beating of the heart
predisposes the patient to a risk of clot formation and stroke.

Anticoagulants thin down the blood and prevent clot formation,
making them the drug of choice for reducing stroke risk in Atrial
Fibrillation.

Despite recommendations, aspirin is still preferred over
anticoagulants in a significant number of these patients, according to a
recent study.

In Atrial Fibrillation, the upper chambers of the heart, known as atria, beat in an irregular fashion, leading to poor blood flow. This can lead to the formation of clots which may travel to the brain and result in a stroke. Therefore, these patients need to be prescribed blood thinners (anticoagulants) to prevent thrombus (clot) formation.

Yet, many of these patients are still being treated with aspirin alone
instead of anticoagulants to reduce stroke risk, according to a recent study
published in the Journal of the American College of Cardiology.

Aspirin Not Effective in Preventing Strokes in Patients With Atrial Fibrillation

The study was conducted by Jonathan Hsu, MD,
at the University of California, San Diego, along with his fellow team members.
They studied the National Cardiovascular Disease Registry (NCDR) Practice
Innovation and Clinical Excellence (PINNACLE) for data of 327656 outpatient AF
patients enrolled between January 2008 to December 2012.

‘It’s the blood thinners and not aspirin that can cut the risk of stroke in atrial fibrillation patients.’

They found out that in the first cohort of
210000 patients with a CHADS2 score (risk score signifying moderate
to high risk for thrombosis) equal to or higher than 2, around 61.8% were
treated with anticoagulants while the remaining 38.2% were prescribed aspirin
alone. In the former group, 90.9% were prescribed warfarin.

The researchers even discovered that certain characteristics predicted the type of treatment received. Patients with a deranged lipid profile, coronary artery disease and history of MI or hypertension were more likely to be treated with aspirin while male patients and those with a history of stroke, systemic embolization, congestive heart failure and higher body mass index were given anticoagulants.

Similar findings were seen on analyzing the second cohort of 294642
patients with a CHA2DS2-VASC score (a score which includes more
CHD risk factors) of 2 or more.

Aspirin Offers No
Stroke Protection

Aspirin is an antiplatelet drug. It prevents platelets from clumping together and forming clots, but it does not act as a blood thinner like anticoagulants. Aspirin can definitely reduce clot formation in the arterial bed but does not offer protection against thrombosis in the heart.

"We know it is a Band-Aid", said Hsu about aspirin, "We know it's
nowhere near as effective as the oral anticoagulant and some evidence suggests
it's not doing anything at all."

Sanjay Deshpande, MD and Samuel Wann, MD from Columbia St. Mary's Hospital, Milwaukee wrote in their editorial titled 'The Clot Thickens' published along with the study that aspirin is ineffective for prevention of thromboembolism associated with atrial fibrillation while oral anticoagulants are far superior in the same. Moreover, aspirin is associated with a risk of bleeding, though small.

Conventionally, aspirin was used to prevent
clot formation in patients with atrial fibrillation and its use, therefore, is deeply
embedded in the minds of cardiologists. The change in the treatment strategy
and the superiority of anticoagulants was realized quite recently after the
following two trials were published:

AVERROES (Apixaban Versus
Acetylsalicylic Acid to Prevent Stroke in Atrial Fibrillation Patients who
have Failed or are Unsuitable for Vitamin K Antagonist Treatment) in 2010,
and

WOEST (What is the Optimal
Antiplatelet and Anticoagulant Therapy in Patients with Oral
Anticoagulation and Coronary Stenting) in 2013.

Need to Educate the Physicians

Editors Deshmukh and Wann noted that while
American Heart Association still slightly supports aspirin use in patients with
low risk of stroke but European Society of Cardiology and NICE in England do
not recommend the use of aspirin to prevent stroke in patients with atrial fibrillation at
all. Therefore, it was surprising to the researchers that even the most meticulous and
talented cardiologists were prescribing aspirin alone in one-third of the
patients.

Lack of awareness regarding the safer new anticoagulants that are associated with a lower risk of bleeding and offer better protection against thromboembolism.

Resistance on the part of the patient to anticoagulants as the drugs are expensive, require following a regimen and are associated with some side effects.

The abstractness of the benefit of stroke prevention which is hard to prove to a reluctant patient.

Thus, there is a need to address both physician-related and
patient-related issues to ensure the appropriate use of anticoagulants in such
patients. The researchers even discovered a wide variability across practices.

The authors therefore wrote, "Focusing on
factors at the practices level, and not simply at the individual physician
level, may prove important in future efforts to rectify proper prescription or
(oral anticoagulation) in (A-fib) patients at risk for stroke."

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